Showing a tooltip via TTM_TRACKACTIVATE does not work - winapi

Question

In a background process I want to display I short message like a balloon in the tray area. However, I do not want to add a tray icon just for that.
Hence I create a tooltip icon and want it to place near the tray.
However, sending TTM_UPDATETIPTEXT, TTM_TRACKPOSITION, TTM_TRACKACTIVATE returns 0. While I am not sure if this should be the case or not, the following code does not show the tooltip window and I don't know why:
This is the code:
// "hwnd" is the HWND to the hidden background window of my background process
HWND hTrayWnd = FindWindow(_T("Shell_TrayWnd"), NULL);
GetWindowRect(hTrayWnd, &trayPos);
HWND hwndTip = CreateWindowEx(NULL, TOOLTIPS_CLASS, NULL,
WS_POPUP | TTS_ALWAYSTIP | TTS_BALLOON,
CW_USEDEFAULT, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT,
hWnd, NULL, NULL, NULL);
LRESULT ret;
TOOLINFO toolInfo = { 0 };
ZeroMemory(&toolInfo, sizeof(toolInfo));
toolInfo.cbSize = sizeof(toolInfo);
toolInfo.hinst = GetModuleHandle(NULL);
toolInfo.lpszText = _T("Test Test");
toolInfo.hwnd = hWnd;
ret = SendMessage(hwndTip, TTM_SETTITLE, TTI_INFO , (LPARAM)_T("Test Title"));
This call returns zero:
ret = SendMessage(hwndTip, TTM_UPDATETIPTEXT, 0 , (LPARAM)&toolInfo); // needs hinst, lpszText, hwnd, cbSize
This call returns zero too:
ret = SendMessage(hwndTip, TTM_TRACKPOSITION, 0, MAKELPARAM(trayPos.left, trayPos.top));
ZeroMemory(&toolInfo, sizeof(toolInfo));
toolInfo.cbSize = sizeof(toolInfo);
toolInfo.hwnd = hWnd;
toolInfo.uId = 1;
And this too:
ret = SendMessage(hwndTip, TTM_TRACKACTIVATE, TRUE, (LPARAM)&toolInfo); // needs hwnd, uId, cbSize
And the tooltip window is never shown.
I also tried to use TTM_ADDTOOL (as suggested in a comment) ad different order of my SendMessage calls but this too returns zero and no tooltip is shown:
LRESULT ret;
TOOLINFO toolInfo = { 0 };
ZeroMemory(&toolInfo, sizeof(toolInfo));
toolInfo.cbSize = sizeof(toolInfo);
toolInfo.lpszText = _T("Test Test");
toolInfo.hwnd = hWnd;
toolInfo.uId = 1;
toolInfo.rect.bottom = trayPos.bottom;
toolInfo.rect.left = trayPos.left;
toolInfo.rect.right = trayPos.right;
toolInfo.rect.top = trayPos.top;
//ret = SendMessage(hwndTip, TTM_ADDTOOL, 0, (LPARAM)&toolInfo);
ret = SendMessage(hwndTip, TTM_SETTITLE, TTI_INFO , (LPARAM)_T("Test Title"));
//ret = SendMessage(hwndTip, TTM_UPDATETIPTEXT, 0 , (LPARAM)&toolInfo); // needs hinst, lpszText, hwnd, uId, cbSize
//ret = SendMessage(hwndTip, TTM_TRACKPOSITION, 0, MAKELPARAM(trayPos.left, trayPos.top));
//ret = SendMessage(hwndTip, TTM_TRACKACTIVATE, TRUE, (LPARAM)&toolInfo); // needs hwnd, uId, cbSize
ret = SendMessage(hwndTip, TTM_ADDTOOL, 0, (LPARAM)&toolInfo);

Answer 1

TTM_TRACKACTIVATE activates a 'tracking tooltip', which is created by setting TTF_TRACK in TOOLINFO::uFlags.